No it is not assigned. IP's are responsible for scheduling their students. Instructors must request their schedules in the scheduling system by 8 AM the previous day. THe schedules are printed and posted around 3 PM each afternoon. THe students wont know with certainty what their schedule will be until the actual schedule is printed out the day before, but they will have an idea of when they are flying becasue this has already been coordinated with their instructor.
What I usually do is discuss with the student at the beginning of the week our plan for the week, and then after each lesson after debriefing, I discuss with the student what day and time I am planning on scheduling them for their next lesson.